Tunable Narrow Linewidth Semiconductor Laser Drive Design

Tunable narrow linewidth semiconductor laser,because of the advantages like the more narrow linewidth,faster wavelength tuning speed,higher output power,well stability output and small dimension,has widely used in optical communication and sensing fields.It also is a well-potential light source applied in resonator fiber optic gyroscope.The accuracy of resonator fiber optic gyroscope depends on the output performance of light source,which is influenced by its driving power.Thus,studying and designing a well performance driving power is of significance for the tunable narrow linewidth semiconductor laser.This thesis aims to design the driving for tunable narrow linewidth semiconductor laser,which has fast wavelength tuning speed and well stability output.The major contents and results can be listed as follows.(1)This thesis studied the rationale and characteristics of the tunable narrow linewidth semiconductor laser.By Testing and analyzing the performance of RIO PLANEXTM series laser,the temperature tuning range of RIO laser is 22.5-26.5? as well as the electric current tuning range is 80-150 m A.By this time,the relationship between its power and electric current can be shown as(35)P(28)0.229 I.The relationship between its power and temperature can be show as(35)P(28)1.145 T.The ratio of wavelength to electric current and to Temperature is and respectively(35)?(28)0.00025 I,(35)?(28)0.01723 T.Apparently,the changed wavelength by the temperature of 1? is bigger than by the electric current of 1m A.So,this thesis is proposed a method by adjusting the temperature change for wide-range tuning and adjusting the electric current for small-range tuning.(2)The temperature control circuit was designed and realized temperature tuning.This thesis designed a temperature control circuit based on MAX1978 temperature control chip.By studying the parameter control of PID,we improve the speed of temperature tuning from 7second to 2s,approximately.The temperature stability is better than 0.005?.(3)The constant current circuit was design and achieved current tuning.We make constant current circuit and current tune circuit on the foundation of circuitry,relevance between current and power,current and wavelength.By using reduction of power supply noise,current stability and current tune stepping achieve 0.075% and 0.055 m A.(4)The design of control electric circuit bases on FPGA.We designed A/D and D/A circuit,A/D minimum sampled voltage is 0.122 m V and minimum output voltage is 0.61 m V.In the meantime,transmission and communication modules based on MATLAB GUI were designed to achieve man-machine communication.(5)The tuning system of laser was tested on the output performance.We measured the temperature stability,current stability,output power stability,wavelength stability and tuning speed by wavelength.The results includes the following: the temperature fluctuation and stability reached 0.002? and 0.008%,the current fluctuation and stability is 0.019 m A and 0.019%,the output power undulation and stability achieve 0.069 m W and 0.86%,and the wavelength variation and stability reached 0.67 pm and 0.43 ppm.Meanwhile,the achieve speed tuned by temperature-wavelength better than 1.8s and tuned by temperature-wavelength is 206?s.